Salt Grass Shale Member.- The Salt Grass Shale Member is a clayey shale containing lime- stone concretions, thin ferruginous concretions, and a few thin layers of bentonite. The most abundant fossil is Baculites eliasi Cobban. The Pierre Shale in western Kansas was formed several hundred miles from the western shore of the Upper Cretaceous seaway and an unknown distance from the eastern shore. The formation is thin in contrast to the much thicker time-equivalent strata farther west in central Colorado. Deposition was probably very slow in Kansas during much of Pierre time, which may account for the abundance of phosphatic concretions and the paucity of fossils in much of the rocks. The fossiliferous limestone concretions in parts of the Weskan suggest that at times bottom conditions were more favorable. LATE CRETACEOUS CYCLIC SEDIMENTATION IN WESTERN KANSAS Formations in the upper part of the Dakota Formation and lower part of the Colorado Group record deposition during the first Late Cretaceous marine sedimentation cycle in Kan- sas. The stratigraphic succession is an asymmetrical cyclothem comprising seven phases including, in ascending order: (1) carbonaceous and commonly clayey siltstone and sandstone and generally silty and carbonaceous gray shale represented by the uppermost part of the Dakota Formation; (2) gray, noncalcareous silty or sandy shale with sandstone beds, repre- sented by the lower part of the Graneros Shale; (3) gray, mostly noncalcareous silty shale with beds of calcareous sandstone and skeletal limestone and local septarian concretions represented by the upper part of the Graneros Shale; (4) shaly chalk and chalky limestone containing relatively little terrigenous detritus, represented by the Greenhorn Limestone and the Fairport Chalk Member of the Carlile Shale; (5) gray, noncalcareous silty shale with septarian concretions, represented by most of the Blue Hill Shale Member of the Carlile Shale; (6) gray, locally concretionary noncalcareous silty or sandy shale with thin sandstone beds, represented by the uppermost part of the Blue Hill Shale Member; and (7) siltstone and sandstone, commonly argillaceous, represented by the Codell Sandstone Member of the Carlile. Macroinvertebrate fossils are abundant only in phases (3) through (5). Lithology, sedimentary structures, and fossils in these beds suggest successive changes from nearshore, shallow, brackish-water deposition in phases (1) and (2) to far offshore deposition in deeper waters of normal salinity in phase (4) and return to nearer shore, shallower water deposition through phases (5) to (7). Cretaceous rock units above the Carlile Shale in western Kansas represent parts of a second major cycle of sedimentation in the eastern portion of the Western Interior Sea. Niobrara strata represent two subphases of maximum transgression analogous to phase (4) of the first cyclothem. 26